He only booked Hendrick for a lunge on Brighton's Rohan Ince when he could easily have sent the midfielder off.

And the hosts were in front 12 minutes later, when Hughes back-heeled Ward's left-wing delivery home for his first goal since 9 November.

Derby, who were last in the top flight in the 2007-08 season, nearly made it 2-0 on the night as Ward charged down Tomasz Kuszczak's attempted clearance, but the ball bounced over the bar.

Derby extend unbeaten run

Derby County have won seven and drawn one of their past eight games

Brighton's top goalscorer Leonardo Ulloa had a chance to pull a goal back when he collected Jesse Lingard's intelligent lofted pass, only to be denied by Lee Grant's excellent save.

Any hopes of a fightback ended in the 56th minute as Martin grabbed his 25th goal of the season following Ward's unselfish header across the face of goal.

Oscar Garcia's side fell further behind on 76 minutes as Thorne volleyed in a spectacular third after Brighton failed to clear Johnny Russell's shot.

It was 4-0 when Hendrick converted after fine work from Bamford, though Lua Lua did at least give Brighton fans something to cheer with a composed finish from the edge of the penalty area.

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Post-match: Derby boss McClaren

This was Derby's day, though, and they can look forward to a trip to Wembley.

They will learn the identity of their final opponents on Monday, when QPR and Wigan play their second leg at Loftus Road after a 0-0 draw at the DW Stadium.

Derby manager Steve McClaren said:

"It is a great achievement by the players. We did not perform as we can on Thursday but they were awesome today, wearing Brighton down with their energy, enthusiasm and bringing the end product as well.

"It is a one-off game at Wembley and if we play like that we are a match for anyone."

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Post-match: Brighton coach Garcia

Brighton manager Oscar Garcia said:

"They were much better than us and deserved the win.

"We have had a lot of injuries and we played the most important game of the season with four or five under-21 players.

"We wanted to give everything and gamble, but it didn't pay off. They are extremely good in front of goal and we did not play very well, but we have no regrets."